if typ.Is(ChecksumIncludesMultipart) {
				wantLen := int(t) * length
				if len(b) < wantLen {
					break
				}
				// Read part checksum
				if part > 0 && uint64(part) <= t {
					offset := (part - 1) * length
					partCs := b[offset:]
					cs = base64.StdEncoding.EncodeToString(partCs[:length])
				}
				b = b[wantLen:]
			}
		} else if part > 1 {
			// For non-multipart, checksum is part 1.
			cs = ""
		}